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Evaluation of Storage Areas in the Salt Creek Watershed

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City of Lincoln

Lower Platte South Natural Resources District

City of Lincoln, NE
Evaluation of Storage Areas
in the Salt Creek Watershed

March 2009

Table of Contents

Cover Page and Table of Contents   (519 K)

Executive Summary   (712 K)

Section 1 - Introduction and Purpose   (418 K)

  • 1.1 Introduction
    • 1.1.1 Salt Creek
    • 1.1.2 Oak Creek
    • 1.1.3 Middle Creek
    • 1.1.4 Wilderness Park
  • 1.2 Goals and Objectives
    • 1.2.1 Existing Data Review
    • 1.2.2 Hydrology and Hydraulics
    • 1.2.3 Storage Area Evaluation
    • 1.2.4 Conceptual Design of Preferred Alternative
    • 1.2.5 Benefit-Cost Analysis
    • 1.2.6 Public Participation (Proposed)
    • 1.2.7 Coordination
  • 1.3 Public Participation Process

Section 2 - Previous Studies and Existing Data   (226 K)

  • 2.1 Previous Studies
  • 2.2 Watershed Inventory
    • 2.2.1 Electronic Files
  • 2.3 Drainage Structures
  • 2.4 Base Mapping
  • 2.5 Salt Creek DFIRM Update
  • 2.6 Groundwater Data Evaluation
  • 2.7 Stream Baseflow
  • 2.8 Airport Issues

Section 3 - Hydrologic Model Development   (1.47 M)

  • 3.1 Introduction
  • 3.2 Hydrology
    • 3.2.1 Subarea Modification
    • 3.2.2 Rainfall
    • 3.2.3 Runoff Volume (SCS CN)
    • 3.2.4 Existing Land Use
    • 3.2.5 Hydrologic Soil Groups (HSG)
    • 3.2.6 Runoff Hydrographs (Lag Time)
    • 3.2.7 Sheet Flow
    • 3.2.8 Shallow Concentrated Flow
    • 3.2.9 Secondary Channel Flow and Primary Channel Flow
    • 3.2.10 Routing (Muskingum-Cunge)
    • 3.2.11 Modeling Results
    • 3.2.12 HEC-HMS Hydrograph Loading
  • 3.3 Hydraulics
    • 3.3.1 Base Map Development
    • 3.3.2 HEC-RAS Geometry File Development
      • 3.3.2.1 Oak Creek Updates
      • 3.3.2.2 Middle Creek Updates
      • 3.3.2.3 Blocked Areas
    • 3.3.3 Unsteady Flow File Development
      • 3.3.3.1 Comparison of Peak Discharges
    • 3.3.4 Methodology for Modeling Offline Storage
  • 3.4 Analysis of Wilderness Park Flood Attenuation

Section 4 - Storage Area Site Description   (821 K)

  • 4.1 Introduction
  • 4.2 Middle Creek
    • 4.2.1 Site Description
    • 4.2.2 Storage Basin Results
  • 4.3 Oak Creek
    • 4.3.1 Site Description - Oak Upstream Site
    • 4.3.2 Site Description - Oak Downstream Site
    • 4.3.3 Oak Creek Storage Basin Results
  • 4.4 Wilderness Park
    • 4.4.1 Site Description
    • 4.4.2 Storage Basin Results
  • 4.5 Haines Branch
    • 4.5.1 Site Description
    • 4.5.2 Storage Basin Results

Section 5 - Storage Area Conceptual Design   (769 K)

  • 5.1 Introduction
  • 5.2 Background
  • 5.3 Conceptual Design
    • 5.3.1 Preliminary Design
      • 5.3.1.1 Middle Creek
      • 5.3.1.2 Oak Creek - Upstream
      • 5.3.1.3 Oak Creek - Downstream
    • 5.3.2 Conceptual Design
      • 5.3.2.1 Middle Creek
      • 5.3.2.2 Oak Creek – Upstream
      • 5.3.2.3 Oak Creek – Downstream
  • 5.4 Spoils Locations

Section 6 - Benefit-Cost Analysis   (54 K)

  • 6.1 Introduction
  • 6.2 Benefit-Cost Analysis Approach
  • 6.3 Benefit-Cost Ratio Calculation Process
  • 6.4 Conclusions

Appendices

Tables

  • 2-1 Structure Data Information
  • 2-2 Average Monthly Stream Baseflow Values
  • 3-1 Subarea Updates
  • 3-2 HEC-HMS Precipitation Input
  • 3-3 Curve Numbers for New Subareas
  • 3-4 Curve Numbers for Salt Creek Watershed Study
  • 3-5 Hydrologic Soil Groups
  • 3-6 New Subarea Lag Times
  • 3-7 Roughness Coefficients (Manning's n) for Sheet Flow
  • 3-8 Muskingum-Cunge Routing Parameters
  • 3-9 HEC-HMS Modeling Results
  • 3-10 HEC-HMS Hydrograph Load Points for New Oak Creek and Middle Creek Reaches
  • 3-11 Oak Creek Structures
  • 3-12 Comparison of Peak Flows and Peak Water Surface Elevations
  • 3-13 Wilderness Park Analysis-100-Year Peak Flow Comparison
  • 3-14 Wilderness Park Analysis-100-Year Maximum Water Surface Comparison
  • 5-1 Middle Creek Offline Storage Elevation Volume Curves
  • 5-2 Middle Creek Modeled Inlet Gates
  • 5-3 Middle Creek Modeled Outlet Gates
  • 5-4 Middle Creek Storage Basins Construction Costs
  • 5-5 Upstream Oak Creek Offline Storage Elevation Volume Curves
  • 5-6 Oak Creek Upstream Modeled Inlet Gates
  • 5-7 Oak Creek Upstream Modeled Outlet Gates
  • 5-8 Oak Creek Upstream Storage Basins Construction Costs
  • 5-9 Downstream Oak Creek Offline Storage Elevation Volume Curves
  • 5-10 Oak Creek Downstream Modeled Inlet Gates
  • 5-11 Oak Creek Downstream Modeled Outlet Gates
  • 5-12 Oak Creek Downstream Storage Basins Construction Costs
  • 6-1 Categories of Avoided Damages
  • 6-2 Benefit-Cost Ratio Procedures
  • 6-3 Total Physical Damages Before Projects
  • 6-4 Total Physical Damages After Projects

Figures

  • 1-1 Locations for Flood Control Storage Areas
  • 1-2 Salt Creek Watersheds
  • 1-3 Wilderness Park
  • 2-1 Oak Creek Well Monitoring Locations (Monitoring Period 1)
  • 2-2 Middle Creek Well Monitoring Locations (Monitoring Period 1)
  • 2-3 Middle Creek Well Monitoring Locations (Monitoring Period 2)
  • 3-1 Updated Subbasins
  • 3-2 Channel Routing Reach
  • 3-3 Updated HEC-RAS Reaches
  • 3-4 Oak Creek Update Cross Sections
  • 3-5 Middle Creek Update Cross Sections
  • 3-6 Modeled Cross Section with Blocked Obstruction
  • 3-7 Cross Section of HEC-RAS Blocked Obstruction
  • 3-8 Wilderness Park Flood Attenuation Scenarios
  • 3-9 Encroachment Analysis Flow Comparison Points
  • 4-1 Possible Offline Storage Sites
  • 4-2 Middle Creek Offline Storage Site Existing Conditions
  • 4-3 Middle Creek Hydrograph
  • 4-4 Oak Creek Upstream Offline Storage Site Existing Conditions
  • 4-5 Oak Creek Downstream Offline Storage Site Existing Conditions
  • 4-6 Air Force Reserve Base Local Subbasins
  • 4-7 Flow and Water Surface Hydrograph at Upstream Oak Site
  • 4-8 Oak Creek Hydrograph With and Without Offline Storage
  • 4-9 Salt Creek Flow Hydrograph Downstream of Oak Creek Confluence
  • 4-10 Wilderness Park Offline Storage Site
  • 4-11 Flow and Water Surface Hydrograph for Wilderness Park Site
  • 4-12 Salt Creek Hydrograph Upstream Cardwell Branch Confluence
  • 4-13 Aerial View of Haines Branch Area
  • 5-1 Offline Storage Areas Analyzed
  • 5-2 Middle Creek Offline Storage Fill and Drain Operation
  • 5-3 Upstream Oak Creek Offline Storage Fill and Drain Operation
  • 5-4 Downstream Oak Creek Fill and Drain Operation
  • 5-5 Middle Creek Inlet Tension Control
  • 5-6 Middle Creek Outlet Tension Control
  • 5-7 Oak Creek Floodway and Conceptual Design
  • 5-8 Oak Creek Inlet Tension Control
  • 5-9 Oak Creek Outlet Tension Control
  • 5-10 Identified Potential Fill Locations
  • 6-1 FEMA Building Depth-Damage Curve
  • 6-2 FEMA Contents Depth-Damage Curve
  • 6-3 Street Flooding Depth-Damage Curve
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